Integrated Gasification Combined Cycle (“IGCC”) systems are an economically attractive alternative to conventional fossil fuel power plants. They present an opportunity to deploy coal, an abundant resource, in an economical and clean manner, bringing improved efficiency over conventional coal-burning steam turbine power generation.
In an IGCC system, a carbonaceous fuel such as coal is converted to a synthetic gas fuel, termed syngas, a mixture formed by partial oxidation at elevated temperatures. Syngas comprises carbon monoxide, hydrogen, and other gaseous constituents. Oxygen-blown gasifiers typically source oxygen from cryogenic Air Separation Units (ASUs) or from Ion Transport Membrane (ITM) Air Separation Units. Cryogenic ASUs employ a combination of compressors, heat exchangers, valves, and distillation columns to effect the separation of oxygen from air at very low temperatures. The cryogenic air separation process consumes significant quantities of electric power, reducing the net plant output and efficiency.
In an ITM air separation process, oxygen molecules in high temperature air, generally in the range of 1400°-1700° F. (760-927 C), are converted to oxygen ions on the cathode side of the membrane, and are transported through the membrane under an applied voltage or pressure differential relative to the anode side of the membrane. Oxygen ions lose electrons on the anode side, reforming into oxygen molecules, with the electrons migrating to the cathode side of the membrane to again ionize oxygen. The membrane elements, being manufactured from ceramic materials, are permeable to oxygen ions at elevated temperatures.